1. Field of the Invention
The present invention relates to an electro-deposition coating composition and an electro-deposition coated member, suited for improving electromagnetic wave shielding effect of optical instruments such as cameras, home electric appliances, or plastic molded housing for office automation machinery, etc.
2. Related Background Art
In recent years, it has been required for cases of electronic machinery to be treated for electromagnetic wave shielding so that electronic machinery can be prevented from misoperation due to electromagnetic wave obstacles. Under such circumstances, as disclosed, for example, in Japanese Patent Application Laid-open No. 59-223763, spray coating making use of a conductive coating material in which a conductive filler is included is prevailing as a method of shielding electromagnetic waves. Other methods are also used, which include zinc spray coating, electroless plating, vacuum deposition and conductive plastic coating.
The conventional methods, however, have the following disadvantages.
The conductive coating material can achieve no sufficient electromagnetic wave shielding effect unless the conductive filler is contained in an amount of not less than 60 parts by weight, and moreover has a coating thickness of not less than 30 .mu.m in the case of a copper filler and not less than 50 .mu.m in the case of a nickel filler. For this reason, it is not suitable for decorative coating of a housing.
The spray coating results in a non-uniform coating thickness when applied to a housing complicated in shape, and also has problems in electromagnetic wave shielding properties and appearance.
As for the zinc spray coating, it gives a coating thickness of as large as from 50 to 100 .mu.m, and also has a difficulty in adhesion properties. For this reason, it becomes necessary to provide steps for blast finishing, etc. In addition, there is still a problem in mass productivity because of a work environment worsened by zinc vapor gas.
In regard to the electroless plating, the whole housing is plated and therefore the exterior of the housing must be subjected to decorative coating on account of appearance. In order to carry out the coating on the surface of the plated housing, a special coating solution must be used since an ordinary spray coating material has such poor adhesion properties between the film surface formed by plating and the coating surface formed by coating that commercial values are lowered. This greatly affects cost and can not be mass-productive.